As fly height decreases in disc drives, it becomes increasingly difficult to maintain a flying interface between the recording head and the disc. Manufacturing variations, environmental conditions such as temperature and altitude, disc topography and other factors can cause mechanical spacing losses. One method to compensate for these spacing losses is to control fly height using electrostatic force. A control voltage can be applied between the entire slider body (or to dedicated slider electrodes) and a disc in order to create an attractive electrostatic force between the slider and the disc. Dedicated electrodes are preferred because they can be designed to avoid contact with the disc and prevent catastrophic failure of the interface caused by “snap-over”. Snap-over occurs when there is a sudden reduction in spacing and the electrostatic force suddenly becomes larger than the air bearing lift force and causes the head to crash. Electrostatic force can increase rapidly when the head-disc spacing is reduced because electrostatic force is inversely proportional to the square of the spacing. Dedicated electrodes also have the advantage that they allow the slider body to be grounded to prevent electrostatic discharge damage to the read-write transducer.
A problem with prior art electrostatic spacing control is that occasional air dielectric breakdown between the electrode and a conducting surface may be impossible to completely eliminate, due to asperities on the conducting surface, loose particles which may pass between the conducting surface and electrode from time to time, or other dielectric breakdowns that crash the head. An arrangement of an electrostatic actuator is needed that can tolerate dielectric breakdown, brief contacts with asperities or loose particles without crashing.
Embodiments of the present invention provide solutions to these and other problems, and offer other advantages over the prior art.